You seem to have your mind pretty made up already but just in case...I do not believe it is a good idea. You have a terrestrial T and I can't imagine there is nowhere in your house where it can't be without being directly under a armful light. If you can take the light, so can the T. Just make sure to provide a piece of bark for her to be able to hide if she feels like it. These Ts are usually active at night and hide during the day so if she is not comfortable with your light she'll hide away. Needless to say that hooking the enclosure to the ceiling might make it more difficult to access and for you to keep an eye on her. Last but not least, hanging it would drastically increase the chance of the enclosure falling (which would very likely be the end of the T).
I would avoid heating mat, it is my personal preference. If you have an ambient temperature in your house of 70 degrees your T should be just fine (a Brachypelma). Although it can get hot during the day for these Ts in their natural habitat, it also get much colder at night (when they are usually more active). So they can tolerate a difference of temperature during the day and night although 50 seems to be getting a bit cold and I am concerned on how the temperature gets to this low in a house where people are living. Break a leg.
